udp(5P)                                                   udp(5P)



     NAME
          udp - Internet User Datagram Protocol

     SYNOPSIS
          #include <sys/socket.h>
          #include <netinet/in.h>

          s = socket(AFINET, SOCKDGRAM, 0);

     DESCRIPTION
          UDP is a simple, unreliable datagram protocol which is used
          to support the SOCKDGRAM abstraction for the Internet
          protocol family.  UDP sockets are connectionless, and are
          normally used with the sendto and recvfrom calls, though the
          connect(2N) call may also be used to fix the destination for
          future packets (in which case the recv(2N) or send(2N)
          system calls may be used).

          UDP address formats are identical to those used by TCP. In
          particular UDP provides a port identifier in addition to the
          normal Internet address format.  Note that the UDP port
          space is separate from the TCP port space (i.e. a UDP port
          may not be ``connected'' to a TCP port).  In addition
          broadcast packets may be sent (assuming the underlying
          network supports this) by using a reserved ``broadcast
          address''; this address is network interface dependent.

     DIAGNOSTICS
          A socket operation may fail with one of the following errors
          returned:

          [EISCONN]      when trying to establish a connection on a
                         socket which already has one, or when trying
                         to send a datagram with the destination
                         address specified and the socket is already
                         connected;

          [ENOTCONN]     when trying to send a datagram, but no
                         destination address is specified, and the
                         socket hasn't been connected;

          [ENOBUFS]      when the system runs out of memory for an
                         internal data structure;

          [EADDRINUSE]   when an attempt is made to create a socket
                         with a port which has already been allocated;

          [EADDRNOTAVAIL]
                         when an attempt is made to create a socket
                         with a network address for which no network
                         interface exists.




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     udp(5P)                                                   udp(5P)



     SEE ALSO
          send(2N), recv(2N), intro(5N), inet(5F).





















































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